1. Field of the Invention
The present invention relates to a package and a packaging method for aqueous liquid materials, and more particularly to a package and a packaging method for aqueous liquid materials wherein a molded container in which an aqueous liquid material has been sealed is sealed within an outer container consisting of an oxygen-absorbent multilayer material. The package and packaging method of the present invention are suitable for the storage of liquid drugs, cosmetics, food products, and other materials whose components are susceptible to oxygen-induced changes. Here, "aqueous liquid materials" is used to mean liquid materials having high water content and high water activity.
2. Description of the Related Art
A conventional method for storing infusion fluids, parenteral solutions, eye drops, oral medication, and other liquid pharmaceutical products, liquid cosmetics, liquid food products, and the like under oxygen-free conditions involves sealing the liquid material in an oxygen-permeable container, and then sealing the sealed container, together with a packet of a deoxidizer, within a bag having gas barrier properties which serves as the outer package. However, due to the nature of liquids themselves, many liquid pharmaceuticals, cosmetics, food products, and other liquids require that the containers in which the liquid will be placed be handled under strict sanitary controls. Conventional methods employing deoxidizer packets have the drawback that is it difficult to maintain sterility of the deoxidizer packets subsequent to sterilization or washing. There is also a risk of the deoxidizer packet being accidentally cut open when sealing the sealed bag which serves as the outer container for the liquid container, causing the liquid container contained therein to be contaminated by the contents of the deoxidizer packet.
Japanese Laid-Open Patent Application 6-83340 discloses an invention which employs in place of a deoxidizer packet an outer packaging bag that has an oxygen-absorbent layer consisting of a deoxidizer dispersed in a thermoplastic resin. However, the oxygen-absorbent layer of the prior art disclosed in this publication has low oxygen absorbing capability, and in order to produce a moisture content sufficient for absorption of oxygen, it is necessary to forcibly induce moisture to permeate into the outer bag from the exterior of the outer bag or the interior of the liquid container through heat sterilization. Accordingly, a heat treatment process was required in order to achieve the desired absorption of oxygen.
Japanese Laid-Open Patent Application 7-171194 discloses a method for introducing the required moisture into a similar outer bag and then enclosing and sealing the liquid container therein. However, the prior art described in this publication has the drawback that the liquid container filled with infusion fluid is wetted by the moisture which has been introduced into the outer bag; this produces an unpleasant sensation when the package is opened for use, and the fact that the package is wet makes it difficult to handle. Further, the moisture introduced into the bag is intended to promote a reaction whereby the oxygen-absorbent layer absorbs oxygen, and reducing the amount of moisture introduced in order to solve the problem noted above causes the rate of oxygen absorption to slow significantly, with the result that considerable time is required to produce an oxygen-free state. During this time, there is a risk of growth of microorganisms nourished, for example, by the glue or similar material used to affix the label to the container, and the outside surface of the liquid container may become soiled by such products. Any attempt to ascertain the minimum water content which will not give rise to such problems requires, in addition to the effort needed to ascertain this level, significant efforts in terms of control of processes such as measuring out the appropriate amounts of water, sanitary controls, and so on.